Peter Frost's anthropology blog, with special reference to sexual selection and the evolution of skin, hair, and eye pigmentation

Friday, May 20, 2011

The demon within. Part III

Sir John Hawkins (1532-1595) was instrumental in bringing England into the slave trade. Was this trade a source of new pathogens for the English population?

Some vaginal strains of Candida albicans have become better at sexual transmission, such as through improved adhesion to saliva-coated surfaces and through displacement of non-vaginal strains in a new host.

But the adaptations don’t stop there. In my last two posts, I argued that these strains have also become better at sexual transmission by manipulating host behavior. They can cross the blood/brain barrier. We know this. Once inside the control room, why not go one step farther?

C. albicans is an ideal candidate for such evolution. First, It’s common. There’s a large pool of genetic variants for natural selection to act upon.

Second, C. albicans has developed the capacity to spread from one host to another through intimate contact. It thus has every reason to enhance this capacity by rewiring its host’s neural circuits, even at the cost of doing much harm.

As biologist Paul Ewald observed:

For decades medical science was dominated by the doctrine of "commensalisms' - the notion that the pathogen-host relationship inevitably evolves toward peaceful coexistence, and the pathogen itself toward mildness, because it is in the germ's interest to keep its host alive. This sounds plausible, but it happens to be wrong.

[…] If you're a germ that can travel from person to person by way of a "vector," or carrier, such as a mosquito or a tsetse fly, you can afford to become very harmful. This is why, Ewald argues, insect borne diseases such as yellow fever, malaria, and sleeping sickness get so ugly. Cholera uses another kind of vector for transmission: it is generally waterborne, travelling easily by way of faecal matter shed into the water supply. And it, too, is very ugly. (Hooper, 1999)

An infectious organism will thus try to turn its host into a launching pad for infection of other hosts. The long-term survival of any one host no longer matters.

Avenues for future enquiry

Where from?

If a pathogen is responsible for cuckold envy, and if the first recorded mention of this fetish comes from 17th-century England, the point of origin is probably extra-European. Specifically, it would have been a society that came into contact with England through that country’s expansion of foreign trade, exploration, and colonization from the 16th century onward. We’re probably looking at the West Indies, West Africa, the eastern American seaboard, or the territories of the Hudson’s Bay Company.

One of my commenters, Jim Bowery, suggested that the pathogen could have entered England via the West African slave trade. Indeed, an argument can be made that sexually transmitted diseases are most likely to develop in high-polygny societies, such as exist among the ‘female-farming’ peoples of sub-Saharan Africa. On the one hand, the polygynous male cannot sexually satisfy all of his wives. On the other, many young males are locked out of the marriage market, the result being a lot of sex on the sly.

As anthropologist Pierre van den Berghe pointed out:

The temporary celibacy of young men in polygynous societies is rarely absolute, however. While it often postpones the establishment of a stable pair-bond and the procreation of children, it often does not preclude dalliance with unmarried girls, adultery with younger wives of older men, or the rape or seduction of women conquered in warfare. Thus, what sometimes looks like temporary celibacy is, in fact, temporary promiscuity. (van den Berghe, 1979, pp. 50-51).

Do other STDs manipulate human sexual behavior?

Is manipulation of sexual behavior a logical adaptation for STDs? If so, have other human STDs evolved in this direction? No one seems to have asked the question. Admittedly, cause and effect are hard to tease apart. Do STDs correlate with sexual promiscuity solely because a promiscuous person is more likely to catch one? Which is the chicken and which is the egg?

Research on insects has turned up several cases of an STD manipulating host behavior in order to facilitate sexual transmission.

Behavioural changes associated with parasitic infection are well known, and at least some of these appear to be adaptations on the part of the parasite to increase transmission (Moore, 1993, 2001; Poulin, 1994a, b, 1998a, 2000). Four recent studies of insect STDs are relevant here. McLachlan (1999) showed that male midges (Paratrichocladius rufiventris) infected with the mite Unionicola ypsilophora were more likely to be in mating pairs than uninfected males. As discussed earlier, the mites rely on female midges to return them to water to complete their life cycle. If they find themselves on a male midge, therefore, they are effectively dead unless their host mates with a female […].

Raina et al. (2000) found that Hz-2V infected female corn earworm moths Helicoverpa zea produce two to three times more sex pheromone than uninfected female moths, possibly enhancing their ability to attract male moths, although they also reported that these animals vigourously resisted mating. Abbot & Dill (2001) found that male Labidomera clivicollis beetles infected with the mite Chrysomelobia labidomera were more likely to displace other males from mating pairs, which again could be interpreted as being adaptive manipulation of the host by the parasite to increase transmission. Webberley et al. (2002), by contrast, found that infection of Adalia bipunctata with Coccipolipus hippodamiae did not have any effect on the mating behaviour of the host. (Knell & Webberley, 2004)

30 comments:

Tod
said...

How about the Caribs as the original source of strains of Candida albicans that cause cuckold envy?They had a long period of isolation and are said to have had unusual immune system characteristics - being particularly well adapted to resist parasites. (10,000 Year Explosion)

Once it got into the African slaves on the sugar plantations of the West Indies strains of Candida albicans could have altered somewhat. Possibly because Africans are particularly vulnerable to parasitic infections.

(Partially due to Africans greater degree of testosteronization - Manning)

I agree that it's possible, perhaps likely, that STDs affect the sex drives of their hosts, but this whole business about cuckold envy seems a bit far-fetched to me.

For one thing, it would be more effective to make the man into a swinger as opposed to a cuckold. Although you say that this particular disease does not transmit well from men to girls, it has to do so at least somewhat effectively, otherwise what would the point be of the girl infecting other men besides her husband or boyfriend?

For another thing, there is a better explanation of cuckold envy which is that it is simply a subset of sexual submissiveness. This explains why your typical cuckold is sitting in the corner instead of having sex with another girl while his wife is with another man.

Anyway, as you point out, for better or for worse it's pretty much impossible to rigorously analyze the effects of STDs on sexual behavior since it's so difficult to separate out cause and effect.

it would be more effective to make the man into a swinger as opposed to a cuckold.

I'm not sure if it would be more effective at facilitating transmission.

It might be easier to induce cuckoldry. You only have to manipulate the direct male host. The infected male lowers his mate guarding behavior, and she moves on and thus infects other men. Or the infected male proposes to his mate that he be cuckolded, and either she leaves him in disgust to meet other men and infect them, or she agrees to participate in the cuckoldry(there's no shortage of other men willing to participate) and thus infects other men.

Turning the male host into a swinger requires not only manipulating the behavior of the direct male host, but also the male's mate (she has to acquiesce to the male being with another woman) and it requires other couples willing to participate in an identical arrangement.

Strains of Candida albicans that cause the strongly maladaptive cuckold envy may be a specifically New World mutation.

The early slave plantations in the West Indies must have been population sinks for the slaves so the cuckold envy strain of Candida albicans may have died out everwhere but England.

I can't see how a sexually transmitted parasite could fail to spread like wildfire in the highly polygynous society of Africa. But then the behavior caused by the parasite would be easy to spot as it would be widely reflected in the culture.

"Turning the male host into a swinger requires not only manipulating the behavior of the direct male host, but also the male's mate (she has to acquiesce to the male being with another woman) and it requires other couples willing to participate in an identical arrangement."

I disagree. Male infidelity has been a lot more accepted in the past. The biblical definition of "adultery" actually means sex between a girl who is married and a man who is not her husband.

And it's much harder to convince a girl to stray than a man. If you don't believe me, experiment with personal ads.

If you're not using the conventional definition of "swinger", and instead using it to mean something like "playboy who sleeps with a lot of women", I'm not sure it would be more likely than inducing cuckold envy.

Virtually all men already wish to sleep with as many women as possible. Assent from women is the limiting factor and a major stumbling block to this desire.

By lowering mate guarding behavior/inducing cuckold envy, it's likely other men will be infected since it's likely the woman leaves and moves on to other men, or stays and agrees to participate in the cuckold fantasy with other men. It's less likely that the woman will stick around in a normal monogamous pair bond after the male lowers mate guarding behavior and or begs her to screw other men in front of him for his own sexual pleasure.

Yes, I was defining it a bit more loosely . . . the idea being that the parties are cool with an open relationship.

"Virtually all men already wish to sleep with as many women as possible."

Well in the cuckold scenario, the man is normally faithful while his wife is sleeping around. Because if both are sleeping around, then it's no longer submissive. In a lot of these fantasies (and probably sometimes in reality), the man does stuff which would make it impossible for him to seduce other girls, such as wearing female clothing or chastity devices.

Well in the cuckold scenario, the man is normally faithful while his wife is sleeping around. Because if both are sleeping around, then it's no longer submissive.

It seems that it'd be easier to induce cuckoldry. You only have to manipulate the direct male host. Whereas turning the host into a playboy stud ultimately requires manipulating strange women external to the host.

"Indeed, an argument can be made that sexually transmitted diseases are most likely to develop in high-polygny societies, such as exist among the ‘female-farming’ peoples of sub-Saharan Africa"

Yes, but there would be far less need for a pathogen to alter behavior in a polygynous society as the large amount of illicit sex (described by Pierre van den Berghe) in such societies would make it really easy for the bug to spread by sexual transmission.

However, when the bug arrived in a society where monogamy was the rule there would be a need for it to manipulate host behavior so as to produce more opportunities for sexual transmission.

I think cuckold envy is a kink of whites, especially professionals with intellectual leanings (see Here).

Whites have high digit ratios and the more educated whites have the highest digit ratios of all. So the pathogen tends to be responsible for cuckold envy in males with low testosteronization.

As the less testosteronized males are found in monogamous societies, in order to spead through a monogamous society a pathogen needs to be adapted to promote cuckold envy in the least testosteronized males (i.e. those who would be expected to be in the most stable relationships). And in fact it does.

So the bug came from a polygynous society and altered to produce cuckold envy once it found inself in the monogamous society of 16th century England.

Infection of the brain by C. Albicans is associated with meningitis. The Jong paper specifically states this. Since the guys that are being infected by C. Albicans as a result of going down on their women are not all dying of meningitis, this theory that C. Albicans infection is turning males into willing cuckolds is unlikely.

C. albicans infection of the brain can lead to meningitis. I would argue that meningitis is the tip of the iceberg, i.e., when the infection goes wrong. The only way to prove this argument would be to examine apparently healthy brains for evidence of C. albicans.

Tod and others,

I'm leaning towards the idea (expressed by several commenters) that there was a long process of coevolution between this hypothetical pathogen and its host population in sub-Saharan Africa. Over time, the host population would have become more insensitive to this neural manipulation.

There is still controversy over the New World origin of syphilis. The strongest evidence is that syphilis was first described in 1530 by an Italian physician, only a short time after the discovery of the New World. But this was also a time when the black slave trade was taking off, and the main destinations of this trade were the plantations of southern Europe, particularly in the Kingdom of Sicily. These plantation economies were later relocated across the Atlantic with the discover of the New World.

As noted above, I was using the word "swinger" loosely, so my point stands. And a man doesn't need to be hugh hefner to have sex with a lot of girls.

The dispute was over what's more likely to develop, lowering mate guarding/inducing cuckold envy or making the man have sex with many women. Probably both of these, along with other, strategies exist in nature under various circumstances. You haven't shown why the latter is more likely to arise than the former. The latter requires manipulating multiple strange women external to the host, or going against monetary and legal limits by seeking prostitutes and or raping women.

"I'm leaning towards the idea (expressed by several commenters) that there was a long process of coevolution between this hypothetical pathogen and its host population in sub-Saharan Africa."

Hmmm, if I follow Prof. Ewald's argument correctly, a sexually transmitted pathogen in a society where there was a lot of sleeping around would evolve towards being more damaging to health. (Quite possibly lethal) Lethal yeast infections ? Not in healthy people.

Candida albicans only kills in late AIDs sufferers (as does Toxo I believe). Nobody really knows where AIDs came from.

"Hmmm, if I follow Prof. Ewald's argument correctly, a sexually transmitted pathogen in a society where there was a lot of sleeping around would evolve towards being more damaging to health. (Quite possibly lethal) Lethal yeast infections ? Not in healthy people."

I don't know about this. I think Ewald's point is that if the strain of pathogen is so lethal it makes the victim sick enough that the host can't spread it to others, then evolution toward a degree of benignity is most likely to occur.

If the pathogen makes people so sick it leaves them immobile and cut off from others, or dead, then it has to have some other means of transmission, a vector like a mosquito or a symptom of the illness that acts as a source of transmission, like diarrhea, that carries the bug on soiled clothes to a source that can spread the bug even further, such as an unclean water supply.

Not all pathogens need to be lethal, after all. The common rhinoviruses seem quite happy to spread themselves among us making us a bit miserable for a week or so but allowing us to feel well enough to spread them.

So, if the bug is lethal and gets away with being lethal, it'll remain so. However, if being lethal threatens its existence or if prospective hosts change the bug's chances of transmission it will, according to Ewald, evolve to benignity to ensure its survival.

Remember that different strains of bugs develop. Peter has suggested a certain strain of this pathogen has develop this ability, but that doesn't mean the bug is so wide-spread it can become lethal--and even if it were omnipresent, that doesn't mean it would, by necessity, have to evolve to being deadly any more than does the common cold virus.

During WW1 lots of young men were crowded into barracks where a bug could spread easily. Lo and behold an incredibly virulent strain of flu emerged. A strain that killed young healthy people at a higher rate than oldsters.

So, the easier it is for a bug to spread the nastier it will be. Conversely if it becomes more difficult for a bug to spread the bug will become less dangerous to health. For example cholera, Ewald's case study is the 1991 cholera epidemic in South America.

"The dots on Saunders's graphs made it plain that cholera strains are virulent in Guatemala, where the water is bad, and mild in Chile, where water quality is good. "The Chilean data show how quickly it can become mild in response to different selective pressures,"

In Africa a sexually transmitted bug would have a relatively easy time of it, hence it would be rather nasty.

But what would happen if that bug found its way to a society where it could not spread so easily. presumably it would become less nasty and more manipulative.

Now, at this point (a strain from a promiscuous society arriving in a largely monogamous society) is where I think the bug would come under strong selection for ways to increase its spread.

The ability to rewire the brain and weaken mate guarding would have been there already. The selection pressure for bugs which took that a step further and produced cuckold envy would not exist to the same extent in a society where promiscuousness is common.

Parasite manipulation for cuckold envy was a late adaptation, it evolved in a monogamous society.

Two of the most commonly reported side effects of chronic Candida infection are lack of libido and fatigue. I have experienced them personally during a long struggle with it. In addition, let's just say that sex during a flare-up is not that appealing. Luckily I was able to get it under control within 9 months of switching to a mostly Paleo diet. My libido gradually went from nearly non-existent to normal.

"I'm leaning towards the idea (expressed by several commenters) that there was a long process of co-evolution between this hypothetical pathogen and its host population in sub-Saharan Africa. Over time, the host population would have become more insensitive to this neural manipulation".

An alternative interpretation: it was the bug that evolved not the host population. Once in a non-promiscuous society the hypothetical pathogen evolved to cope with a new situation.

After all, it is the capacity for extremely rapid evolution which allows parasites to evolve manipulation. Considering that yeast evolves several orders of magnitude faster than humans it is difficult to see how co-evolution could work.

Bug-host co-evolution could work because the pathogen's damage to the host is often incidental. The pathogen is being selected for its ability to spread to other hosts. The host is being selected for its ability to contain the damage.

The selective equilibrium is much less in the host's favor than in a situation where the pathogen cannot easily spread to another host. In that situation, the bug is both jailer and prisoner. Nevertheless, I still see the possibility for some co-evolution: the bug gets to spread and multiply and so does the host.

Kurt,

There are many examples of pathogens that colonize neural tissue without going ballistic. The bug is being selected for its ability to take over the control room, not for its ability to trash it.

Peter, Thanks for the responses to my convoluted and constantly shifting line of argument. Here is yet another rejoinder.

How could a bug increase the man's reproductive fitness while increasing the chance he will be cuckolded ? It couldn't.

"Bug-host co-evolution could work because the pathogen's damage to the host is often incidental"

The man gets infected and the more the bug brings about cuckold envy in that man the more it damages the reproductive fitness of that man. So in a sense the bug could be very very nasty indeed and the man would not suffer any obvious ill effects. By my way of thinking that kind of 'damage' is most certainly not incidental it is inherent to the mode of tranmission you ae hypothesizing (ie manipulation of the man for enhanced tranmission through his female partner).

The damage would be contained. The polygynous male would just be indifferent to cuckoldry. He would no longer be actively assisting it, and he would still derive pleasure from having sex with his own mate (s).

In a mating environment with many sexual partners and low paternal investment, that isn't such a bad deal. It becomes a bad deal if you have only one mate and you're investing a lot in her children.

It seems to me that targeting the mate guarding system is needlessly complex. Biochemically, it's much simpler to just increase the sex drive. In light of that, it's surprising, that we haven't ALREADY seen the evolution of an STD that changes the behavior of the host in that exact fashion.

Interestingly rabies makes people hypersexual, and in males, likely to commit rape. Victims can become infected by the sexual contact or by neckbites that occur during the assault, and become rabid themselves (the resemblance of this to vampires may not be a coincidence, google rabies vampire explanation).

"..."Hypersexuality may be a striking manifestation of rabies," Gomez-Alonso wrote in his article, adding that "the literature reports cases of rabid patients who practiced intercourse up to 30 times in a day...."

But rabies is so virulent that victims are generally dead in a few days after the rage begins. Still... that's a microbe that can make someone extremely horny, at least for a few days. So it's at least hypothetically possible that someday an STD may arise, that makes people hypersexual without killing them or interfering with reproduction; such a microbe would quickly become widespread.

Or perhaps it already happened, tens of thousands of years ago, and our infection rate has been 100% for all recorded history, so we don't have a baseline to realize what we're "supposed to" be like....

It seems to me that targeting the mate guarding system is needlessly complex. Biochemically, it's much simpler to just increase the sex drive.

Increasing sex drive to rape can be risky though. It can be punished with death by the state, by revenge, by the victim's male relations going after the rapist, as has often been the case throughout history.

Perhaps something like targeting mate guarding arose in response to pressures against rape.

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